The invention relates to an optical scanning device for scanning an optically scannable information carrier, which scanning device is provided with a radiation source, an optical lens system having an optical axis for focussing a radiation beam supplied, in operation, by the radiation source into a scanning spot on the information carrier, an actuator for displacing the lens system with respect to a base part of the scanning device in a direction parallel to the optical axis, and an adjusting member for setting an inclination of the lens system with respect to the information carrier, the lens system being elastically suspended from a suspension member which, viewed in a direction transverse to the optical axis, is arranged next to the lens system, while the adjusting member is provided with a first part and a second part, which can be displaced with respect to the first part.
The invention also relates to an optical player comprising a table which is rotatable about an axis of rotation, an optical scanning device comprising an optical lens system for scanning an optically scannable information carrier which can be placed on the table, and a displacement device by means of which, during operation, at least the lens system of the scanning device can be displaced substantially in a radial direction with respect to the axis of rotation.
An optical scanning device and an optical player of the types mentioned in the opening paragraphs are disclosed in U.S. Pat. No. 5,703,864. The known optical player including the known optical scanning device employed therein is particularly suited for scanning optically scannable information carriers with a relatively high information density, such as DVD. To scan such information carriers in the right way, the inclination of the lens system with respect to the information carrier, i.e. the deviation from the right angle which the optical axis includes with respect to the information carrier, should remain within predetermined relatively narrow limits. In the manufacture of the optical scanning device, such a deviation develops as a result of manufacturing tolerances, particularly as a result of manufacturing tolerances in the lens system""s elastic suspension from the suspension member. For this reason, the inclination of the lens system is adjusted once only with respect to a reference information carrier, by means of the adjusting member, after the manufacture of the optical scanning device. In the known optical scanning device, the second part of the adjusting member is provided on the base part on which also the suspension member and a stator part of the actuator are provided. The first part of the adjusting member is provided on a main frame of the optical scanning device. To minimize the structural height of the known optical scanning device, viewed in a direction parallel to the optical axis, the actuator is arranged, viewed in a direction transverse to the optical axis, next to the lens system, while the adjusting member is arranged directly below the lens system, viewed in a direction parallel to the optical axis. To keep a radiation beam path clear, the second part of the adjusting member is provided on a stepped support of the base part, which support is situated directly below the lens system.
A drawback of the known optical scanning device and the known optical player resides in that the stepped support of the base part leads to a relatively complicated construction of the scanning device and, viewed in a direction parallel to the optical axis, limited freedom of movement of the lens system.
It is an object of the invention to provide an optical scanning device and an optical player of the types mentioned in the opening paragraphs, wherein, viewed in a direction parallel to the optical axis, a minimum structural height is provided, as in the prior art, but the above-mentioned drawback of the known optical scanning device and the known optical player is obviated as much as possible.
To achieve this object, an optical scanning device in accordance with the invention is characterized in that the second part of the adjusting member is provided on the suspension member, while the first part of the adjusting member is provided on a supporting member which is arranged next to the lens system, viewed in a direction transverse to the optical axis.
To achieve this object, an optical player in accordance with the invention is characterized in that the optical scanning device used therein is an optical scanning device in accordance with the invention.
As a result of the fact that in the optical scanning device in accordance with the invention, the second part of the adjusting member is provided on the suspension member, while the first part of the adjusting member is provided on said supporting member, the adjusting member is positioned, viewed in a direction transverse to the optical axis, next to the lens system, so that, viewed in a direction parallel to the optical axis, the structural height of the optical scanning device is substantially not influenced by the presence of the adjusting member. Since the adjusting member is situated next to the lens system, viewed in a direction transverse to the optical axis, the adjusting member is at a distance from a radiation beam path of the optical scanning device, so that further constructional adaptations to preclude that the adjusting member obstructs the radiation beam are not necessary. In addition, the adjusting member in said position does not influence the freedom of movement of the lens system in a direction parallel to the optical axis.
A particular embodiment of an optical scanning device in accordance with the invention is characterized in that the supporting member is arranged in a fixed position with respect to the base part and a stator part of the actuator. Since the supporting member is arranged in a fixed position with respect to the base part and the stator part of the actuator, the operation of setting the inclination of the lens system with respect to the information carrier by means of the adjusting member also influences the inclination of the lens system, and of a translator part of the actuator attached thereto, with respect to the stator part. As the stator part is arranged, in this particular embodiment, in a fixed position with respect to the base part, the stator part can be accurately positioned with respect to the base part and with respect to a position of the information carrier, during the manufacture of the optical scanning device. By virtue thereof, both the inclination of the lens system with respect to the information carrier and the inclination of the translator part of the actuator with respect to the stator part can be simultaneously set within desired limiting values at a later stage using the adjusting member.
A further embodiment of an optical scanning device in accordance with the invention is characterized in that the first part of the adjusting member is provided with a first supporting surface having a component which extends at right angles to the optical axis, which first supporting surface is provided in a fixed position on the supporting member, and with a second and a third supporting surface which each have a component which extends at right angles to the optical axis, and which are in positions, with respect to the supporting member, which can be adjusted, viewed in a direction parallel to the optical axis, while the second part of the adjusting member is provided with a first, a second and a third supporting element, which bear against, respectively, the first, the second and the third supporting surface under the influence of a pretensioning force originating from an elastic pretensioning element, the second and the third supporting surface being arranged on either side of the first supporting surface, and a distance between the optical axis and an imaginary line through the second and the third supporting surface differing substantially from a distance between the optical axis and the first supporting surface. By using said three supporting surfaces and said three supporting elements, it is achieved that the inclination of the lens system with respect to the information carrier can be readily and accurately adjusted. As said three supporting elements bear against said three supporting surfaces under the influence of a pretensioning force, a degree of freedom of the suspension element parallel to the optical axis, and degrees of freedom of the suspension element with the lens system suspended therefrom about two inclination axes extending at right angles to the optical axis are fixed in a statically determined way. By adjusting the positions of the second and the third supporting surface over equal distances and in the same direction, viewed in a direction parallel to the optical axis, the inclination of the lens system about a first inclination axis is set, which first inclination axis is at right angles to the optical axis and parallel to the imaginary line through the second and the third supporting surface. By adjusting the positions of the second and the third supporting surface over equal distances and in opposite directions, viewed in a direction parallel to the optical axis, the inclination of the lens system about a second inclination axis is set, which second inclination axis is at right angles to the first inclination axis and the optical axis.
Yet another embodiment of an optical scanning device in accordance with the invention is characterized in that the second and the third supporting surface are each provided on an adjusting screw which can be turned with respect to the supporting member. By using adjusting screws, the inclination of the lens system with respect to the information carrier can be set in a simple and accurate way. The inclination thus set can be readily and reliably locked by locking the adjusting screws with respect to the supporting member by means of, for example, an adhesive.
A particular embodiment of an optical scanning device in accordance with the invention is characterized in that the first part of the adjusting member is provided with a fourth and a fifth supporting surface, which are substantially situated in an imaginary plane parallel to the optical axis, and are provided in fixed positions on the supporting member, and with a sixth supporting surface, which extends perpendicularly to the fourth and the fifth supporting surface and parallel to the optical axis, and which is provided in a fixed position on the supporting member, while the second part of the adjusting member is provided with a fourth and a fifth supporting element, which bear against, respectively, the fourth and the fifth supporting surface under the influence of a pretensioning force originating from the pretensioning element, and with a sixth supporting element for cooperation with the sixth supporting surface. By using the fourth, the fifth and the sixth supporting surface and the fourth, the fifth and the sixth supporting element, also two degrees of freedom of the suspension element, which are mutually perpendicular and extend at right angles to the optical axis, and a degree of freedom of the suspension element, with the lens system suspending therefrom about, the optical axis are fixed in a statically determined way.
A further embodiment of an optical scanning device in accordance with the invention is characterized in that the first part and the second part of the adjusting member are provided with, respectively, a seventh supporting surface and, cooperating therewith, a seventh supporting element by means of which the sixth supporting surface and the sixth supporting element can be held in position with respect to one another. By using the seventh supporting surface and the seventh supporting element, the pretensioning element does not have to supply a component of the pretensioning force which is directed at right angles to the sixth supporting surface, resulting in a simplification of the construction and attachment of the pretensioning element.